KingRex of Taiwan markets two USB Y cables. Those occupy two type A sockets on the computer end, one type B on the DAC side. That keeps data and power lines on physically separate legs. Not only that, it affords the option of jacking the power leg not into the computer but KingRex's optional $189 uPower battery supply. uPower runs two 3.75V Sanyo Lithium-ion cells with a linear voltage regulator to output a clean 5V DC. Such a scheme short-circuits dirty computer power from getting anywhere near the D/A converter circuitry. Think of it as retrofitted galvanic isolation for bus-powered USB transceivers.

KingRex of course aren't usually in the wire business. Hence for this project they've smartly outsourced quality raw ingredients from those who are. The $495/2m red uArt cable is based on a conductor bundle from a high-profile US specialist, the $649/2m blue uCraft is a Japanese equivalent. KingRex assembles these conductor bundles into their chosen Y configuration, then terminates them with quality 24K/1μ gold-plated plugs in CNC'd red-anodized aluminum casings filled with unspecified damper material. For good measure they then cryo-treat their builds at -196°C/-320°F for molecular strengthening.
"Our labor for USB Y cable production is very very high. These cables are 100% hand-built in Taiwan. Adding the isolation netting, soldering, adjustments and damper fill, each technician can only do 3 straight or one Y-shaped cable in a working day." Either KingRex cable conforms to the USB 2.0 high-speed spec for data transfer up to 480mbps.

This divide & conquer approach to signal & power purity on the universal serial bus also shows up in the $895 earlier Acoustic Revive cable. More are bound to follow. The concept makes sense. With an obvious proviso. Your DAC's USB transceiver must ride on USB power. The XMOS board on my Eximus DP1 does slurp USB juice. Ditto the original Cypress Semiconductor-based hiFace built into my massive APL Hifi NWO-M player. Ditto the XMOS board inside the Meitner MA-1 I reviewed some time back. Meanwhile my recently upgraded NWO-M now sports an XMOS-based OEM hiFace 2. And that's driven exclusively from internal power. Ditto Linnenberg Audio's u:c:a with its original hiFace augmented by custom auxiliary circuits. Such machines consume zero USB power [see basic schematic for u:c:a below]. They are thus utterly immune to the charms of battery shenanigans. They're in fact allergic.

I first encountered this with the u:c:a. Even its designer couldn't explain why. Leashed up to the battery-fied KingRex cable, his DAC was invisible to OS Lion in my usual iMac. Only when the power lead was reseated in the iMac did the u:c:a appear to it as a selectable output device. The same happened with Alex Peychev's upgraded NWO-M. Why it should matter is a riddle. Not that you would spring for the uPower supply with a non-bus powered USB transceiver in the first place. It simply turns out that if you did, it actually wouldn't work.

Today's uCraft Y runs silver-plated OFC copper conductors, a twin shield of tin-plated wire and aluminum tape, a polyolefin dielectric and a blue PVC sheath. The internal geometry is referred to as "inverted concentric". Like the uArt, the flat ribbon-type cross section only bends two ways and twists very reluctantly. KingRex claims that "after cryo treatment and adding DC power, the native sonic differences of these two cables enlarge". Usage is straightforward. With two very obvious provisos. If you invert power and signal ends to plug the signal lead into the battery supply, no sound (the plugs feature clear symbols to indicate which is which). If you forget to charge the battery supply or run it down, no sound either. Should that happen, simply reseat the power lead in your computer until the battery is live again.

In a prior review on five USB cables, I'd been faced by a 4+1 grouping. Four weren't identical but so closely grouped as to not much matter. Only one was clearly superior to stand out. That had been the red-faced KingRex uArt. Already convinced that the company was on to to something, I agreed to take Mr. Blue for a spin and report on whether he overtook Mr. Red or went sideways into merely different turf. If I could even tell 'em apart...